Thermoplastic resins, and in particular poly(lactic acid) resins which are biodegradable polyester resins, appear promising for use as packaging materials such as containers and films, as textile materials for garments, floor mats and automotive interior materials, and as molding materials in the production of housings and components for electrical and electronics products. Polyolefin resins are widely used in materials for the necessities of daily life and in various types of industrial components, such as automotive interior and exterior components. The range of polyolefin resin use has grown particularly in automotive interior and exterior components, such as bumpers, instrument panels, door trim and pillars.
In order to improve the processability and heat resistance of thermoplastic resins, including such poly(lactic acid) resins and polyolefin resins, efforts are being made to increase the rate of crystallization and degree of crystallization of these resins. One such approach involves adding a crystal nucleating agent. A “crystal nucleating agent” serves as the primary crystal nuclei for crystalline polymer and promotes crystal growth; hence, it functions to make the crystal size finer and also increases the rate of crystallization.
For example, crystal nucleating agents for poly(lactic acid) resins that have been disclosed include inorganic particles composed of talc and/or boron nitride of having a particle size less than a specific particle size (Patent Document 1), amide compounds of a specific formula (Patent Document 2), sorbitol derivatives of a specific formula (Patent Document 3), phosphoric acid ester metal salts and basic inorganic aluminum compounds (Patent Document 4), and metal salts of phosphorus compounds of a specific formula (e.g., phenylphosphonic acid metal salts) (Patent Document 5).
Also, metal salts of phosphonic acid, phosphonous acid and the like are available as effective crystal nucleating agents for poly(etherester) block copolymers (Patent Document 6).
In addition, carboxylic acid metal salts, such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and sodium bicyclo[2.2.1]heptane-2,3-dicarboxylate; phosphoric acid ester metal salts such as sodium bis(4-tert-butylphenyl)phosphate and sodium 2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate; compounds such as polyol derivatives, including dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol; and metal salts of, for example, aromatic phosphonic acids and aromatic phosphonous acids have been proposed as crystal nucleating agents for polyolefins (Patent Document 7).